Reflecting means



April 20 1926.

T. c. RHODES REFLEQTING MEANS Sheets-Sheet 2 I 2 a J I [N VE/VT'OR 5. E w. H. N w m m w w .m

19TTORNEY-J April 20 1926'.

7 c. RHODES REFLECTING MEANS Filed July 26, 1922 5 Sheets-Sheet 5 3} INVENTOB T/ULOB CHLHOUN RHODES by 03mm A'TTOR/Vrra April 20 1926. 1,581,491

T. CLRHODES: REFLEcTIN MEANS Fil y 1922 v 5 Sheets-Sheet 5 .Zivazwrae, 72'); 0e (army/v 6940411 Patented Apr. 20, 1926.

UNITED STATES TAYLOR CALHOUN RHODES, or are. PAUL, mmnnsozm.

' REFLECTING MEANS.

Application filed m 26,

To all whom it may concern:

Be it known that I, TAYLOR CALHOUN Ri-ronns, a citizen of the United States, and a resident of St. Paul, in the county of Ramsey and State of -Mimiesota, have invented certain new and useful Improvements in Reflectine Means, of which the following is a specification.

One object of my invention is to provide a reflector of such construction that substantially all of the lightfrom a source of light, hereinafter referred tofas bulb, used therewith will be projected forwardly and so directed as to fall where needed for giving the best illumination.

' Another object is to provide a reflector so adapted'as to have a bulb positioned within the reflector at the focal point of the re-- flector, the characteristics of the inner curved surface of the reflector being such that all light, except that thrown directly forward from the bulb to the desired field of light, will itself be reflected from one curved surface of the reflector to another and thence to the focal. oint of the reflector, and will. either pass through a second similar series of reflections so as to be, or will then be forwardly. thrown from the focal point co-incident with those rays which are not reflected, but. which pass through an opening to this field of light.

Another obyect is to provide a bulb having a filament therein substantially at the focal point of the bulb, the shape of the bulb being such that when it is surroundedjby a reflector having a similar contour or is coated either inside or outside by a reflecting substance over such portion of its surface as corresponds to the above described reflector,

said reflector will reflect all light fallen thereon through the focal point of the bulb in the same manner as above described.

' In general the objects of my invention are to provide a combination of reflectors that will as nearly as possible gather all the rays of light from the source of light except those that fall in a given field of light and reflect the rays so gathered through the source of lightand co -incident with the rays that fall into the desired held of light.

Vith these andincid'ental objects in view, the invention consists of certain novel features of construction and combination of parts. the essential elements of which are hereinafter described with reference to the 1922. Serial No. 577,659.

drawings which accompany and form a partof'this specification.

In the drawings:

Figure 1 is a vertical section taken, I

showing the manner in which rays are di-- pected through the focal point of the reflec- .or; Figure? is a schematic diagram illustratmg the position of a plurality of suppositious flatmirrors as described in reference to the development of the contour of my reflector;

Figure 8 is a schematic view of a special construction of the reflector designed 'to throw all of the light upon the road ahead and below a predetermined height and also in equal volumes upon equal road distances;

, Figure 9 is a schematic view of the reflector of the style shown in Figure 8 and illustrating the manner in which the light rays may pass through'the focal point of the reflector to cast equal volumes upon equal road distances;

Figure lO is a composite view partially in rear elevation of the reflector shown in F ig ure 9 and partially in vertical section on the line 1010 of Figure 9;

Figure '11 is a vertical section taken through the longitudinal axis of a modified construction of my invention in which the lamp bulb itself is made in the shape desired for the reflector and is tightly enclosed in a reflector. shell, or may be coated by reflecting material on irner or outer surfaces, except that portion thereof which corresponds to the opening of the reflector.

Figure 12 is a diagram used in describing the theory of equal areas of light;

Figure 13 is a diagram showing the development of the tangents to which the irregular curve of my reflector may be drawn.

In the selected'embodiment of the invention shown in Figurel, the-lamp body 15 in any of their adjusted positions.

received within the bayonet socket 21. The

socket is carried by a hollow threaded stem 22adjustably supported by the body 15.

The stem 22 is received in threaded engagement with the nut 23, the annularly flaring head of whichis supported by the lower wall of the lamp body 15. The exterior of the shank of the nut 23 is square and extends through the circular aperture in the lower wall.' The nut 23 may be adjustably r0- tated by means of a driving ring 24 which is exteriorly hexagonal and interiorly square to receive the shank of the nut 23 therethrough. This ring 24 is also of a diameter greater thanthe aperture. The aperture in the lamp wall is large enough to permit horizontal displacement of the nut 23 for the desired adjustment of the bulb. The head of the nut 23 and ring 24 are sufficient- 1y large to close entirely the wall aperture A look nut 2 5 -is' received in threaded engagement on'the stem 22 and holds all parts in adjusted position. Obviously, the length of the stem of the nut 23 must be less than the sum of the thickness of ring 24 and wall 15. The screw and nut adjustment 17 is adapted to hold thereflector 16 in a plurality of ad-' justed positions and is substantially similar in construction and operation to the ad]ust ment of the stem 22.

On a plane perpendicular to the horizontal axis of the reflector at its focal point 27,

two pairs of minute holes 40-40 are drilled diametrically opposite each other; one pair being in upper right and lower left quadrants and the other at right angles thereto. By sighting through these holes the filament of the bulb may be properly ad]usted within the focal point'of-the reflector. Holes 50 are drilled in lamp body '15 in like relation to the focal point of the lens 20 to be used therewith. They may be threaded and closed b screws. By lining up holes 40 and 50, the ocal point of the reflector is made to coincide with the focal point of the lens.

Then by lining the filament of the bulb with holes 40 and 50, the bulb, reflector and lens are in common focus.

A direct ray of light 32 froinfocal point 27 is bent bylens 20 into a ray 33, parallel with the axis of the reflector! Ray 26 ema- .will refer to as the reflected light.

The portion of reflected light which orig inates in a cone symmetrical and opposite to the direct cone of light will be referred to as negative rays and the rest of the reflected light, as positive rays.

It will be seen that all the positive reflccted light will, by two reflections, be cast forwardly through the focal point coincident with the direct rays of light; and that all the negative cone of reflected light, which is equal in volun'ie to the direct cone of lightwill, by a series of four reflections, 'befcast forwardly through the focal point coincident with the direct rays of'light. Therefore, the average number of reflections for the direct light plus the negative is two, and as the positive, light is reflected twice, the average number of reflections for all the light is two.

In the diagram Figure 6, the direct cone of-light' is included within the angle 35. The positive ray of light 36 strikes the reflector at the portion 37, is reflected therefrom to the portion 38 of the surface of the reflector and thence, 1 'sses through the focal point 27, and out in the same path 39 as does a portion of the direct cone of light.

Consideringnow another positive ray 4'13 It will be noted that this ray strikes the portion 42 of the reflecting surface, is reflected therefrom to the surface portion 43 and passes through the focal point 27 and- A typical negative my 45 of the reflected light will strike the portion 46 of the reflecting surface, will be reflected therefrom to the surface portion 47- and thence through the focal point 27 joining with the positive ray 36, to the portion 37 on the reflecting surface. From here it will be reflected to the portion 38 of they reflecting surface'and thence through the focal point 27 and will pass out through the opening 34 within the direct cone of light along the path .39.

It will be seen that all reflected light will eventually be reflected about the interior of the reflector so as to pass through the focal point 27 of the reflector and hence out through the opening 34, merging with the unreflected rays so that with the exception of the light lost or absorbed all of the light from the focal point of the bulb will eventually pass out through the opening 34. If a lens is used as shown in Figure 1, then in as which is placed the filament 49. Therefore,

When the bulb, except for the portion 34, corresponding to the opening in the front 'end of the eggshell reflector, is surrounded by a reflecting shell 51 of the same shape, the result obtained is the same as that proviously described with reference to Figure 6. The course of light may be shown by the positive light ray 52 reflected by the portion 53 of the reflecting surface to the reflecting surface portion 54 fro-m which it passes through the focal point 27 and continues outwardly through the opening 34 in the direct" cone of light.

Figure 8 shows another type of reflector embodying the same general principles and to be used as a-headlight for automobiles,

etc., although it appears to be different from the type previously described, it is the same combination of a lateral and a rear mirror developed to one angle combined with parts of a lateral andrear mirror. developed to another angle to make an unsymmetrical finished unit. This type is designed to dis: tribute all of the light rays below a horizontal plane passing through the focal point 27 and to have this light evenly distributed along the road in front of the headlight. To accomplish this I make the reflector unsymmetrical with respect to its horizontal aXis--in other words somewhat lopsided as shown by the shell 55.

The line 99 representsthe road laid off in equal lengths by lines perpendicular thereto. The-radial lines from the focal point 27 meet these perpendiculars at the road line, in varying angles 87 to 92. The space between angle 92 and the horizontal axis of the reflector may be divided into angles nearly equal to angle 92 or any other proportion desired.- The lines bounding angles 87 to 98 are projected rearwardly through the focal point 27 and so limit the amount of light which will be cal-led negative reflected light and divide it into the-same number of corresponding angles. -;-The rest of the light from focalpoint 27 isdivided into the same number of equal volumes. The equal volumes of light are reflected through the various angles 87 to 98, and fall upon equal road distances or go further forward as predetermined by the angles 93 to 98. The theory of this reflecting surface is the same as the other construction in that it is so triangular paths into the direct shaped that all reflected light, no matterthe focal point 27 passes out through the opening 56 in the usual manner, shaped as a half cone, and a positive ray 57 will be reflected from the surface 58 to a surface 59, thence through the focal point- 27 and out through the opening 56 along the path 60. Similarly a positive ray 61, will be reflected from the surface at 462 to the surface at (53, thence through the focal point 27 and out through-the opening 56 along the path 6%. The negative light is .reflected through two light as it was in Figure 6.

It will thus contemplates a single reflector which may be considered as being composed of an infinite number of reflecting surfaces, the focal reflector they will be so reflected about theinterior surface of the reflector that they will eventually pass through this focal point and. thence out through the opening probe seen that the invention vided and will beprojected forwardly coincident with the direct rays.

Having described my invention and illustrated it in various ways, I will now take up the manner in which the .contour of the reflector is developed and shall first explain the theory of equal volumes of light in adjacent cones of light in connection with the diagrammatic View of Figure 12, and shall then discuss the theory of reflection and laying out by trial method the proper curve for the reflector in connection with the diagrammatic view of Figure 13. Theory of equal volwmes of light adjacent cones of light. a The initial steps for producing the irregular curve shown by a longitudinal sect on taken through the axis of my reflecting shell are shownv in Figure 12 and may be de scribed .as-follows:

With the center of the filament of a bulb as the center 1 of the drawing, a vertical-- line 2"3"is drawn through 1 and is the point 5' and of a length such that the distance 56? equals the distance 5"8, represents the cross-section of the desired field of light if intercepted at a point a distance :from the center of the bulb equal to 1-5.

As 6' and 8 are the top and bottom limits of the field, line 61 and 8l, would if revolved on the axis 4'5 limit a cone which represents the direct light to be thrown forward to field 68 by the bulb at 1 Revolve lines 181' and l61 (which are extensions of straight lines 81 and 6'1') on axis 45 and they will limit a cone oflight at 18-1'16 which is equal to and symmetrical with the direct cone of light.

On theaxis 45 lay'ofl' any convenient number of equal distances each wa from the point 1'. The more of these d visions used the more true a reflector curve will be developed. In thiscase four units are laid off each Way at points 20, 21, 22', 23 and Vertical lines are erected through these points" perpendicular to the axis 4=--5. A circle with point 1 as its center is drawn thru the intersectionsof lines at 20 and 28 with the lines 818t and 6 and 16 at points 30 and 40' and 38 and 48'. This intersects the other vertical lines at points 31 to 37' inclusive and -41 to 47' inclusive. Extended radial lines a'redrawn through these various points of intersection from point 1 which lines shall be known as lines 30 to 38' and 40 to 48.

Revolving this plane drawing upon its horizontal axis 4' 5, would cause the various radial lines to bound cones each of which would have its apex at point 1. The ortions of the area ofthe sphere bounde by the planes developed by the parallel lines perpendicular to the axis are in the same ratio, one to another, as the distance between the parallel planes and in this case are equal. That part of the area of the sphere Which lies within the cone whose apex 1s the center of the sphere is a correct measureof' the spherical volume of light radiated-from the spheres center within the cone and may hereinafter be called the volume of the cone of light. The volume of cone of light to the volume of cone of light 311 -t1 less the volume of cone of light 30-140. It is also equal to the volume of cone of light 33::v-"1 -4:3 less the volume of cone 32'142'; also equal to the volume of hemisphere of light 34'144 on the left hand less the volume of the cone -of light 33'1'43. In other words the various angles between two adjacent lines limit equal spherical volumes of light from the center I of the shpere developed by rotation of the circle, except the cone of light which lies in the field of light and its opposite.

Line 3949 is drawn tangent to the circle already drawn and parallel to line- 30"40. These lines are perpendicular to the horizontal axis 45. The space between lines 3040 and 39-49"i's divided by lines parallel thereto into eight equal divisions. These lines will intercept the circle through these points from point 1 will, if revolved as set forth in the preceding paragraphlimit cones of light in which the dif ference between volumes of' two cones of light bounded by adjacent lines will equal the volume of the central cone of light 57" 167.

The last mentioned group of radial lines which pass through the center 1 and are extended to pass through the forward part of the circle cut it at points 70 to 7 8 and to 88; 70 lying in the same line as 50; 71 as 51'; 72 as 52; 80 as 60; as 61' and 82' as 62', etc.

WVe now have the plane cross-section of the sphere divided into angles by lines radi ating from its-center, which lines, if revolved completely around the axis 4-5', will out each of the portions of the spheres surface developed by are 7078, arc 60-68' into Discussion of theory of reflection and laying out by trial method the proper curve for the eggshell shaped reflector.

It is well known that in the reflection of light from a mirror the angle of reflection is equal to the angle of incidence and that a line perpendicular to the surface of a flat mirror will bisect the angle between the ray of light which falls upon the mirror and the ray of light reflected therefrom.

If then, light falls on a mirror and another fiat mirror be set in the path of the y ray of light falling upon the first point andror in the plane.

reflected light and so placed as to reflect this reflected light back to the source of light, the light follows a triangular path from the source to the first mirror thence to the second mirror and thence to the source of light. These three lines-of direction of the light will hereinafter be referred to as the triangular course of light and the first path be known as side A, the second as side B, and the third as side C of the triangle. The source of light will be designated at 1 and is in the focal point 27 of the reflector; the first mirror will be designated as the lateral mirror or L, and the second mirror as the rear mirror or R. I

The bisector of the angle made by lines A- and B is the perpendicular to the mirror L. The bisector of the angle made by lines B C is a perpendicular to the mirror R.

Therefore, to direct a ray of light from a given source falling upon a given point, to another point, bisect the angle made by the a line from that point to the second point. Erect a plane perpendicular to the bisector at the point of the angle and place-the mir- Lines in Figures same relation to those as do those in Figure 12, bear the same numbers in the second power instead ofthe first power. In Figure 13 let line 1 -30 be the side A of thefirst triangle. At any point on this line, such as point 30 draw a line perpendicular to the axis l -5 to a point on the line 1 50 which will now be p0int5O In Figure 8 let line 1 80 be the side A of the first triangle. At any point on this line, such as point 30 draw a line which shall meet the axis at a point 50 Pointv 50 shall be in this figure, on the axis 4 -5 The angle 30 -501 shall be less than a right angle. It will be noted that in Figure 8, line 50 1 and the axis 4 5 are identical; point lies on the axis 4 5 and that points 40 and 50 are identical. The following description applies to Figures 8 and'l3,'except that in Figure 8 the second triangle has not been illustrated. This line is the second line of the triangular course of light or line B. Line 1 5O is the third line or line C.

The bisector of the angle 1 3O -.50 is the line 30 -30". The perpendicular to 30 .30 is 30 or a lateral mirror. The light from this mirror follows-the sideof the triangular course of light B to point 50 There a rear mirror is placed to direct the light back to the center 1 along line C. The bisector of the angle 30 --501 is the line 50'50 The perpendicular to this bisector is the line 5O -50 which determines the location o f the rear mirror for the triangular course of light 1 -3O -5O 1 This triangular course of light carries light in both the fols and 13 an. bear the method ca n be followed to develop the curves for Flgure 8, except that the various radial lines within the lines A and C would conform to the rearward extension through point 27 of the rays 87 to 98. On line l -31 a trial point 31 'is selected for thelocation of the lateral mirror. This point will be nearer to the center 1 than is the intersection of lateral mirror 30 with the line 31 and nearer to the center 1 than is the point 31 Point 31 is then used as a oint for a second lateral mirror which shal reflect the light from center "1 along line 31 to a point 51 on .line 51 Line 31 31 is a bisector of the angle 131 -51. Line 31 is perpendicular 'to this bisector and is the second lateral mirror.

Point 51 is nearer the center 1 than is. Y

the intersection of the rear mirror 50 with the line 51. '1 and farther than is the point 51 Line 51 51" is the bisector of the angle Line 51 'is perpendicular-t0 this bisector and is used as the rear mirror for this triangular course of light.

If thetrial points used cause'the mirrors 31 and 30 to intersect each other at a point nearly equidistant from points 30? and 31 and the rear mirrors 50 and 51 to intersect each other nearly equidistant from on lines 32 .-1 and a-point on line 52 -1 1 and repeat the samemethod for developing another pair of lateral and: rear mirrors.

These mirrors must bear the same relation to 31 and 51* that 31 and 51 bear to of short flat mirrors which re-reflects the light to the original source of light at/the focal point and forwardly through the same, coincident with the direct rays of v1i ht which fall upon Negative light will also be reflected through the desired fieldof li g tn points 50 and 51 or so'that each lateral v for each of the -folscribed.

' sired, a

a new reflector designed with the radial linestwo triangular paths hereinbefore de- By increasing the number of radial lines the flat mirrors become, smaller and increase in number proportionately. By drawing on a very large scaleand using small divisions the mirrors can be brought to very small size. Then by' using the mirror surfaces as- -tangents draw a I lpair of curves through the intersections wit the radial lines. These curves will not bere'gular curves-but slow spirals.

By rotating the curves thus formed around the axis 4 5 the curves will meet at poin'ts'30 and close together the rear-and sides, leaving open only that portion which lies within the forward cone of light -1 -8O Thus the contour of the egg-shell reflector is developed. 4

In Fi re 7 there are shown six triangular paths 0 light and their lateral and rear mirrors upon which, two curves may be drawn, using the mirrors, as tangents. Revolving these curves around the axis would develop the contour of the novel egg-shell reflector. v

This method of developin curves applies when the top, bottom and si es are all to be symmetrical; namely, when the field of light is to be round and have equal distribution of light over equal areas equidistant from the center of the field. It should benoted that o nings limiting direct cones of light 'ofdi erent angles have been shown in the drawings and be developed light.

If more light is to be placed in one half of the field than in the other, the top'lateral and bottom rear mirrors must be developed together and the bottom lateral and top rear mirrors together, in the same genthat the egg-shell reflector can for different sized fields of eral way as above described, but by using relation as to give the radial lines in such desired proportion of light over the field. In Figure '8 the top'half of the field, i. e. above the axis, receives no reflected light, and all of the reflected light is concentrated in the lower half of the field; and it will also be noted that the line SO -40 will not be perpendicular to the axis but at an angle which-may be found by trial, that will cause both upper and lower rear mirrors to coincide.

If the test reflector when completed does not give the exact proportion of light dephotometric test shpuld be made and which bound the rays 87 tov 98 slightly changed in proportionate relation so that the more light may be placed in too dim areas and vice versa to bring the light to the distribution originally desired. 1

Thus if the my 90 is too weak, the radial lines from I which bound ray 90 should be brought closer together so as to concentrate the same amount of light into a smaller area ance of the rays would be enlarged or dev creased in uniform ratio to account for the surplus 'or diminished space.

While I have described my invention and illustratedit in several designs, I do'not wish it understood that I limit myself to this construction, as it is evident that the application of the invention may be varied in many ways within the scope of the following claims:

1. A reflector substantially of egg-shell shape having a single focal point and adapted to have a source of light positioned substantially at said focal point, the reflector having an opening at one end adjacent said focal point, saidopening to be of a dimension sufiiciently large to permit free passage of all light rays emanatin from said source of light and tending to fa upon the desired field of light, and saiddimension being sufficiently limited to cause .the reflector to intercept all light rays so emanatin except those tending to fall'upon said fie d.

2. A reflector having a single focal point and having an o ening at one end adjacent to said focal point, the interior. surface of coincident with the direct rays passing through said opening.

3. In a reflector means having a single focal point and comprised of a plurality of rear mirrors merged one into the other and a plurality of lateral mirrors merged one into the other, said mirrors being so positioned that all lights thrown upon a lateral mirror from or through a source of light positioned at the focal point of the reflector, will be reflected to a rear mirror and thence through the source of light to the desired field of light, and all the light thrown upon a rear mirror will be reflected to a lateral mirror and thence to and through the source of light to an opposite lateral mirror. and thence to a rear mirror. and back through illhehsource of light to the desired field of 4. In a reflector of general egg-shell shape, the combination with the inner reflecting surface thereof, of a source of light positioned at the focal point of said reflector, the contour of the inner surface of the reflector being such that. all light radiated from the focal point and received by-the inner surface ofthe reflector will be reflected through the focal point by a plurality of reflections, the last'reflection throwing all the reflected light through the focal point and thence out the 5. In a reflector means, the combination of a reflector of general eg -shell shape having a single focal point adjacent an opening at its smaller end toward the desired field of light, a source of. light positioned at the focalpoint of said-reflector, the contour of the inner surface of said reflector being such that a portion of the light from said source will pass directlyjo said field of light and that all the other light will be reflected within said reflector, except that lost in absorption, and will be reflected back through said focal point andout to said field of light.

. 6. In a reflector apparatus, the combination of a reflecting means adapted closely to fit an electric lamp bulb of substantially eggshell shape, sai d reflecting means providlng a reflector having a single focal point within the bulb adj went the small end thereof, said reflector having an bpening at the small end thereof to permit passage of light.

7. A light reflector adapted to be positioned about a source of light and shaped to provide an irregularly curved internal reflecting surface having a single focal point, a source of light at said focal point, the reflector having an aperture adjacent to said focal point whereby all internally reflected rays pass through the source and outwardly through the aperture.

In witness whereof, I have hereunto set my hand this 17th day of July 1922.

TAYLOR CALHOUN RHODES. 

